Chair base



FIG. 1 is a left side, top perspective view of a chair base, showing mynew design;

FIG. 2 is a right side, bottom perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a right side elevation view thereof;

FIG. 7 is a top plan view thereof;

FIG. 8 is a bottom plan view thereof; and,

FIG. 9 is another perspective view thereof, shown in a position of use.

The broken lines are shown for the purpose of illustrating both parts ofthe chair base as well as environmental subject matter. None of thebroken lines form part of the claimed design.

CLAIM The ornamental design for a chair base, as shown, and described.